Great attention is focused on electrical powered vehicles such as an electric vehicle and hybrid vehicle as environment-friendly vehicles. These vehicles incorporate an electric motor for generating a driving force for running, and a rechargeable power storage device for storing electric power to be supplied to the electric motor. A hybrid vehicle refers to a vehicle incorporating an internal combustion engine as a power source, in addition to an electric motor, or a vehicle further incorporating a fuel cell in addition to a power storage device as the direct current power source for driving the vehicle.
Among the hybrid vehicles there is known a vehicle that allows charging of the vehicle-mounted power storage device from a power source external to the vehicle, likewise with an electric vehicle. For example, the so-called “plug-in hybrid vehicle” is known that allows the power storage device to be charged from a general household power supply by establishing connection between the plug socket located at an establishment and the charging inlet provided at the vehicle through a charging cable.
As a method for power transfer, attention is recently focused on wireless electrical power transmission without using power supply cords and/or cables for electrical transmission. Three promising approaches of this wireless power transfer technique are known, i.e. power transfer using electromagnetic induction, power transfer using electromagnetic waves, and power transfer through the resonance method.
The resonance method thereof is a non-contact power transfer approach transferring power via an electromagnetic field by causing resonance at a pair of resonators (for example, a pair of self-resonant coils) at the electromagnetic field (near field), allowing electric power as high as several kW to be transferred over a relatively long distance (for example, several meters) (refer to Non-Patent Document 1).
Patent Document 1: WO 2007/008646
Non-Patent Document 1: Andre Kurs et al., “Wireless Power Transfer via Strongly Coupled Magnetic Resonances”, [online], Jul. 6, 2007, SCIENCE, Volume 317, pp. 83-86, [Searched on Sep. 12, 2007], Internet <URL; http://www.sciencemag. org/cgi/reprint/317/5834/83.pdf>